There seems to be a flood of fantasy ideas at this site - dreams of anti-gravity and technological impossibilities. It would be nice if some sort of technological capability was included with suggestions.

yes, this is a wonderful idea, as long as this magic knife tech is given to us eventually by the aliens...

I forsee a problem if it is zapped and its programming reverses. It could start killing people!

Yes, but. How would you stop it going stright through the cutting board, and the table underneath, ...

There is the story of the man, who after years of research, discovered the perfect solvent. It dissolved everything. Then he spent the rest of his life trying to discover a bottle to keep it in.

Sorry for being a cynic.

Admittedly, the concept is good. It is the technology which is daunting. What is required is an educated knife with a form of regulations taken from Asimov's three rules of robotics. Knives are very difficult to educate. I have a few knives in my kitchen and I cannot even get them to say "good morning" to me at breakfast. This, of course, is merely the first step.

On what level is this knife supposed to distinguish between human flesh and animal meat? Will it also not cut my nails accidentally? And at what threshold does it stop being a flesh-friendly knife and start being a thrown object that will most certainly hurt regardless?

This idea is great!!! I propose an idea to create a carying case that will hold, not only this wonderfull knife, but also my gun that will only kill bad people.

Though I agree with most of the comments, a strange irony is that a potato peeler is a knife designed to not be able to cut people.

I still prefer to peel potatos with a regular paring knife.

What about a light saber that detects what material it touches and then decides if it should cut through it. Depending on its programing!!! sorry if it sounds like im mocking u, but maybe when light sabers come out this could be an option